When planning a flight against the wind, how to you pick the best
altitude when trying to minimize flight time?

If I read my performance charts correctly, my aircraft (Piper Turbo
Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
*true* airspeed for every 1000 feet you go up. Firstly, does that sound
about right to folks? I assume that this effect is from the decrease in
air friction at high altitudes (even though the prop also has less air
to "push on").

So, unless there is some other factor, I think this means that if the
winds increase at anything higher than 2 nts per 1000 feet, I am best
off staying at the Minimum Enroute Altitude. Is that right?

My experience thus far suggests that most of the time, the winds aloft
speed increase far faster then 2 nts per 1000 feet, so, in general, it
is unlikely that I will do much better than staying at the absolute
minimum altitude. Is that consistent with other folks' experience?

-Sami

when I plan a flight against the wind (like a few days ago comming back from
phoenix) I go with the altitude that gives me the best ground speed.
On my way back from phoenix at 8500 ft I had a GS of 130 kts, I had to go to
10500 for terrain and my GS went down to 117 kts., so I jumped back down to
8500 when I had the chance.

Turbo airplanes take advantage of the thinner air up high is why they can go
faster then normally aspirated planes. you maintain your full 200 HP up to a
DA of 12,000 ft. So 12000 ft is where you start to lose horse power but the
air is thinner allowing you a better TAS and if you play the winds right,
some really good ground speeds. stay low if you have a head wind, get up
high when you have a tail wind.

Sometimes, the wind down low will be higher then say around 10,000 or 12000
ft or about the same. If there is not much difference in the winds, I would
select the higher altitude because of the thinnner air. Also you dont use as
much fuel up high.


"O. Sami Saydjari" wrote:

> When planning a flight against the wind, how to you pick the best
> altitude when trying to minimize flight time?
>
> If I read my performance charts correctly, my aircraft (Piper Turbo
> Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> *true* airspeed for every 1000 feet you go up. Firstly, does that sound
> about right to folks? I assume that this effect is from the decrease in
> air friction at high altitudes (even though the prop also has less air
> to "push on").
>
> So, unless there is some other factor, I think this means that if the
> winds increase at anything higher than 2 nts per 1000 feet, I am best
> off staying at the Minimum Enroute Altitude. Is that right?
>
> My experience thus far suggests that most of the time, the winds aloft
> speed increase far faster then 2 nts per 1000 feet, so, in general, it
> is unlikely that I will do much better than staying at the absolute
> minimum altitude. Is that consistent with other folks' experience?
>
> -Sami

I travel about 8-10 thousand into the wind and 14-20 with the wind. I agree.
Usually the headwind increases faster than TAS with altitude. I travel 8-10
for safety--glide distance.



"Jeff" > wrote in message
...
> when I plan a flight against the wind (like a few days ago comming back
from
> phoenix) I go with the altitude that gives me the best ground speed.
> On my way back from phoenix at 8500 ft I had a GS of 130 kts, I had to go
to
> 10500 for terrain and my GS went down to 117 kts., so I jumped back down
to
> 8500 when I had the chance.
>
> Turbo airplanes take advantage of the thinner air up high is why they can
go
> faster then normally aspirated planes. you maintain your full 200 HP up to
a
> DA of 12,000 ft. So 12000 ft is where you start to lose horse power but
the
> air is thinner allowing you a better TAS and if you play the winds right,
> some really good ground speeds. stay low if you have a head wind, get up
> high when you have a tail wind.
>
> Sometimes, the wind down low will be higher then say around 10,000 or
12000
> ft or about the same. If there is not much difference in the winds, I
would
> select the higher altitude because of the thinnner air. Also you dont use
as
> much fuel up high.
>
>
> "O. Sami Saydjari" wrote:
>
> > When planning a flight against the wind, how to you pick the best
> > altitude when trying to minimize flight time?
> >
> > If I read my performance charts correctly, my aircraft (Piper Turbo
> > Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> > *true* airspeed for every 1000 feet you go up. Firstly, does that sound
> > about right to folks? I assume that this effect is from the decrease in
> > air friction at high altitudes (even though the prop also has less air
> > to "push on").
> >
> > So, unless there is some other factor, I think this means that if the
> > winds increase at anything higher than 2 nts per 1000 feet, I am best
> > off staying at the Minimum Enroute Altitude. Is that right?
> >
> > My experience thus far suggests that most of the time, the winds aloft
> > speed increase far faster then 2 nts per 1000 feet, so, in general, it
> > is unlikely that I will do much better than staying at the absolute
> > minimum altitude. Is that consistent with other folks' experience?
> >
> > -Sami
>

"O. Sami Saydjari" > wrote in message >...
> When planning a flight against the wind, how to you pick the best
> altitude when trying to minimize flight time?
>
> If I read my performance charts correctly, my aircraft (Piper Turbo
> Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> *true* airspeed for every 1000 feet you go up. Firstly, does that sound
> about right to folks? I assume that this effect is from the decrease in
> air friction at high altitudes (even though the prop also has less air
> to "push on").
>
> So, unless there is some other factor, I think this means that if the
> winds increase at anything higher than 2 nts per 1000 feet, I am best
> off staying at the Minimum Enroute Altitude. Is that right?
>
> My experience thus far suggests that most of the time, the winds aloft
> speed increase far faster then 2 nts per 1000 feet, so, in general, it
> is unlikely that I will do much better than staying at the absolute
> minimum altitude. Is that consistent with other folks' experience?

The 2 kts per 1000 feet seems about right. The speed increase is due
to the fact that the turbo allows the engine to maintain power output
at a much higher elevation than a normally aspirated engine. The
increased power output coupled with thinner air allows the plane to go
faster.

Generally speaking, the winds above 10k are out of the west, and can
be strong enough to negate the speed advantage of the turbo. On these
trips, it makes sense to fly lower. Going Eastbound, you will
generally want to fly high to take advantage of both the high TAS and
the large tailwinds.

There are exceptions however, so you need to look at the forecast and
PIREP'ed winds aloft as part of your flightplanning to decide whether
or not it makes sense to climb high.

However, you will find many times that having a turbo and oxygen are a
great advantage no matter what the winds aloft. Just last week, I was
on top of a rising cloud layer at 10,000 in my Cherokee, a smooth ride
and in the sun. (The clouds were ~9kft thick at my location.)
However, as I traveled North, I was to pass a weak cold front, and the
temps were already dropping. I considered climbing higher, but had
visions of my Cherokee struggling to outclimb iceladen clouds, and of
course the hypoxia issues as one continues climb... I ended up
descending and flew 2 hrs in bumpy, rainy IMC. Not much fun, but I
kept the OAT above zero and made it to my destination no problems.

If I had turbo and oxygen, I would have zipped up to 12,14,16,
whatever it took to clear the clouds, enjoyed a smooth ride home in
the sun, and an easy descent in the better weather at my destination.

-Nathan

"O. Sami Saydjari" > wrote in message
...
> When planning a flight against the wind, how to you pick the best
> altitude when trying to minimize flight time?
>
You need to run the performance charts against some actual weather. Use
ADDS for wind and everything else. Up wind and downwind are completely
different exercises. Every day is different but patterns will quickly
develop with experience. The turbo changes things a bit. Hit the books
with some actual weather.

In article >, "O. Sami Saydjari"
> writes:

>So, unless there is some other factor, I think this means that if the
>winds increase at anything higher than 2 nts per 1000 feet, I am best
>off staying at the Minimum Enroute Altitude. Is that right?
>

Yes, but it is generally smoother up higher.

Chuck

In a previous article, said:
>When planning a flight against the wind, how to you pick the best
>altitude when trying to minimize flight time?

Since Santa was good to me and I now have the complete Sporty's Air Facts
on DVD, I've now seen Richard Collins say several times that he chooses
his altitude based on finding a smoother ride rather than a faster trip.
Of course, he's got a pressurized and turbo charged P-210, so he's got a
lot more choice of altitude than I do.


--
"The magic of usenet has never been its technology; and, only in part, its
reach. Its magic -- its power -- is based on the very real human connections
that form 'round its threads of conversation... the relationships that are
kindled, flamed and, on occasion, extinguished and mourned." -deCadmus

Lazy people (like me) ask their computer. FlightStar from Jepp has an
"optimize altitude" function that is pretty handy. Once it has downloaded
DUATs weather it will display groundspeed and fuel burn for all altitudes
and highlight the optimal flight level.

"O. Sami Saydjari" > wrote in message
...
> When planning a flight against the wind, how to you pick the best
> altitude when trying to minimize flight time?
>
> If I read my performance charts correctly, my aircraft (Piper Turbo
> Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> *true* airspeed for every 1000 feet you go up. Firstly, does that sound
> about right to folks? I assume that this effect is from the decrease in
> air friction at high altitudes (even though the prop also has less air
> to "push on").
>
> So, unless there is some other factor, I think this means that if the
> winds increase at anything higher than 2 nts per 1000 feet, I am best
> off staying at the Minimum Enroute Altitude. Is that right?
>
> My experience thus far suggests that most of the time, the winds aloft
> speed increase far faster then 2 nts per 1000 feet, so, in general, it
> is unlikely that I will do much better than staying at the absolute
> minimum altitude. Is that consistent with other folks' experience?
>
> -Sami
>

I generally run several flight plans at different altitudes, accounting for
the differences in true air speed, wind speeds, and time to climb and
descend. More often than not, I find that the extra time to climb uses up
the gains in TAS at altitude, and winds are the only factor that make a
significant difference. If the flight is long, say 3-4 hours, then the
climb can be worth it, but for less than a couple of hours, it usually is
not. I fly behind a turbocharged engine and have built-in oxygen, so I can
go anywhere up to 18-20K, but usually stay below 12K or so unless there is a
net advantage due to wind. I like to stay high enough to keep from having
to switch from centers to approach controls all the time and to get above
the haze layer for a smoother ride. But sometimes the high winds just force
you down into the turbulence and traffic at 3-4K.

Stan

"O. Sami Saydjari" > wrote in message
...
> When planning a flight against the wind, how to you pick the best
> altitude when trying to minimize flight time?
>
> If I read my performance charts correctly, my aircraft (Piper Turbo
> Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> *true* airspeed for every 1000 feet you go up. Firstly, does that sound
> about right to folks? I assume that this effect is from the decrease in
> air friction at high altitudes (even though the prop also has less air
> to "push on").
>
> So, unless there is some other factor, I think this means that if the
> winds increase at anything higher than 2 nts per 1000 feet, I am best
> off staying at the Minimum Enroute Altitude. Is that right?
>
> My experience thus far suggests that most of the time, the winds aloft
> speed increase far faster then 2 nts per 1000 feet, so, in general, it
> is unlikely that I will do much better than staying at the absolute
> minimum altitude. Is that consistent with other folks' experience?
>
> -Sami
>

McGregor > wrote:
: Lazy people (like me) ask their computer. FlightStar from Jepp has an
: "optimize altitude" function that is pretty handy. Once it has downloaded
: DUATs weather it will display groundspeed and fuel burn for all altitudes
: and highlight the optimal flight level.

Although I can do it by hand, I find it much more convenient to have DUATS do
it for me. Since I fly a non-turbo'd Cherokee, I'm effectively relegated to 10kft or
less. A quick check of winds aloft, and maybe two or three altitudes with DUATS flight
planner (it corrects for current wind) and see where I end up. On the fly, I pretty
much figure I need about 5 kt difference in wind to counteract a 2000' climb/descent.
Unfortunately, the nicer the weather (this time of year in particular), the higher the
pressure and bigger the headwind for a westly flight is. Even skimming the trees at
1000' AGL doesn't usually help, so I end up climbing for smoothness and happy engine at
6-10k.

-Cory


--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

I went to Jeppeson's website and looked up flitestar. Looks like a nice
software package. What I could not find is pricing information for the
software or the subscription service to keep the charts updated and
such. Can you give your view on the software and let us know what it
retails for (including any subscriptions). Thanks.

-Sami

McGregor wrote:
> Lazy people (like me) ask their computer. FlightStar from Jepp has an
> "optimize altitude" function that is pretty handy. Once it has downloaded
> DUATs weather it will display groundspeed and fuel burn for all altitudes
> and highlight the optimal flight level.
>
> "O. Sami Saydjari" > wrote in message
> ...
>
>>When planning a flight against the wind, how to you pick the best
>>altitude when trying to minimize flight time?
>>
>>If I read my performance charts correctly, my aircraft (Piper Turbo
>>Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
>>*true* airspeed for every 1000 feet you go up. Firstly, does that sound
>>about right to folks? I assume that this effect is from the decrease in
>>air friction at high altitudes (even though the prop also has less air
>>to "push on").
>>
>>So, unless there is some other factor, I think this means that if the
>>winds increase at anything higher than 2 nts per 1000 feet, I am best
>>off staying at the Minimum Enroute Altitude. Is that right?
>>
>>My experience thus far suggests that most of the time, the winds aloft
>>speed increase far faster then 2 nts per 1000 feet, so, in general, it
>>is unlikely that I will do much better than staying at the absolute
>>minimum altitude. Is that consistent with other folks' experience?
>>
>>-Sami
>>
>
>
>

O. Sami Saydjari wrote:
> When planning a flight against the wind, how to you pick the best
> altitude when trying to minimize flight time?
>
> If I read my performance charts correctly, my aircraft (Piper Turbo
> Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> *true* airspeed for every 1000 feet you go up. Firstly, does that sound
> about right to folks? I assume that this effect is from the decrease in
> air friction at high altitudes (even though the prop also has less air
> to "push on").
>
> So, unless there is some other factor, I think this means that if the
> winds increase at anything higher than 2 nts per 1000 feet, I am best
> off staying at the Minimum Enroute Altitude. Is that right?
>
> My experience thus far suggests that most of the time, the winds aloft
> speed increase far faster then 2 nts per 1000 feet, so, in general, it
> is unlikely that I will do much better than staying at the absolute
> minimum altitude. Is that consistent with other folks' experience?
>
> -Sami
>

Yes, generally lower is better in high wind conditions such as winter
across much of the US. However, you need to balance speed against
turbulence which also tends to be worse at low altitudes, at least over
mountainous regions.

Matt

Stan, It guess I was too lazy to try to compute the flight plan several
different ways. Your note, and one other made me dust off the math
knowledge and do some of that there fancy ciphering (hearing "weeeee
dogies" in the background...said with hillbilly accent, of course).

For a mythical plane that climbs 1000 fpm at 100 nm/hr and cruises at
150 nm/hr and a service ceiling of 20,000 ft. Comparing flight at 1000
ft agl versus 18,000 agl....for a 100nm trip one's tailwind would have
to be about 40nm better at 18,000 compared to 1000 ft. For a trip
distance of 200, the tailwind would only need ot be about 14nm/hr more
favorable. For a 700 mile trip (one that I will be making fairly
often), the winds only need to be about 3nm/hr more favorable.

Now, I just hope the mythical heater is powerful enough so that I do not
freeze my butt off at those altitudes.

-Sami

Stan Prevost wrote:
> I generally run several flight plans at different altitudes, accounting for
> the differences in true air speed, wind speeds, and time to climb and
> descend. More often than not, I find that the extra time to climb uses up
> the gains in TAS at altitude, and winds are the only factor that make a
> significant difference. If the flight is long, say 3-4 hours, then the
> climb can be worth it, but for less than a couple of hours, it usually is
> not. I fly behind a turbocharged engine and have built-in oxygen, so I can
> go anywhere up to 18-20K, but usually stay below 12K or so unless there is a
> net advantage due to wind. I like to stay high enough to keep from having
> to switch from centers to approach controls all the time and to get above
> the haze layer for a smoother ride. But sometimes the high winds just force
> you down into the turbulence and traffic at 3-4K.
>
> Stan
>
> "O. Sami Saydjari" > wrote in message
> ...
>
>>When planning a flight against the wind, how to you pick the best
>>altitude when trying to minimize flight time?
>>
>>If I read my performance charts correctly, my aircraft (Piper Turbo
>>Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
>>*true* airspeed for every 1000 feet you go up. Firstly, does that sound
>>about right to folks? I assume that this effect is from the decrease in
>>air friction at high altitudes (even though the prop also has less air
>>to "push on").
>>
>>So, unless there is some other factor, I think this means that if the
>>winds increase at anything higher than 2 nts per 1000 feet, I am best
>>off staying at the Minimum Enroute Altitude. Is that right?
>>
>>My experience thus far suggests that most of the time, the winds aloft
>>speed increase far faster then 2 nts per 1000 feet, so, in general, it
>>is unlikely that I will do much better than staying at the absolute
>>minimum altitude. Is that consistent with other folks' experience?
>>
>>-Sami
>>
>
>
>

I was thinking real hard about that glide distance the other day flying to
phoenix.
when passing over the colorado river area, I felt my plane kinda "surge", never
felt it before, I thought the engine was surging but didnt see any indications
on any of my instruments. I was looking around for a place to land and 8500 ft
just didnt look high enough at the time.
the trip was unevenful tho, I am thinking it was a gust of wind hitting me from
behind making the plane surge forward for a second.

Wyatt Emmerich wrote:

> I travel about 8-10 thousand into the wind and 14-20 with the wind. I agree.
> Usually the headwind increases faster than TAS with altitude. I travel 8-10
> for safety--glide distance.
>
> "Jeff" > wrote in message
> ...
> > when I plan a flight against the wind (like a few days ago comming back
> from
> > phoenix) I go with the altitude that gives me the best ground speed.
> > On my way back from phoenix at 8500 ft I had a GS of 130 kts, I had to go
> to
> > 10500 for terrain and my GS went down to 117 kts., so I jumped back down
> to
> > 8500 when I had the chance.
> >
> > Turbo airplanes take advantage of the thinner air up high is why they can
> go
> > faster then normally aspirated planes. you maintain your full 200 HP up to
> a
> > DA of 12,000 ft. So 12000 ft is where you start to lose horse power but
> the
> > air is thinner allowing you a better TAS and if you play the winds right,
> > some really good ground speeds. stay low if you have a head wind, get up
> > high when you have a tail wind.
> >
> > Sometimes, the wind down low will be higher then say around 10,000 or
> 12000
> > ft or about the same. If there is not much difference in the winds, I
> would
> > select the higher altitude because of the thinnner air. Also you dont use
> as
> > much fuel up high.
> >
> >
> > "O. Sami Saydjari" wrote:
> >
> > > When planning a flight against the wind, how to you pick the best
> > > altitude when trying to minimize flight time?
> > >
> > > If I read my performance charts correctly, my aircraft (Piper Turbo
> > > Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> > > *true* airspeed for every 1000 feet you go up. Firstly, does that sound
> > > about right to folks? I assume that this effect is from the decrease in
> > > air friction at high altitudes (even though the prop also has less air
> > > to "push on").
> > >
> > > So, unless there is some other factor, I think this means that if the
> > > winds increase at anything higher than 2 nts per 1000 feet, I am best
> > > off staying at the Minimum Enroute Altitude. Is that right?
> > >
> > > My experience thus far suggests that most of the time, the winds aloft
> > > speed increase far faster then 2 nts per 1000 feet, so, in general, it
> > > is unlikely that I will do much better than staying at the absolute
> > > minimum altitude. Is that consistent with other folks' experience?
> > >
> > > -Sami
> >

I was looking at flight star, is it as good as jepp says it is?

McGregor wrote:

> Lazy people (like me) ask their computer. FlightStar from Jepp has an
> "optimize altitude" function that is pretty handy. Once it has downloaded
> DUATs weather it will display groundspeed and fuel burn for all altitudes
> and highlight the optimal flight level.
>
> "O. Sami Saydjari" > wrote in message
> ...
> > When planning a flight against the wind, how to you pick the best
> > altitude when trying to minimize flight time?
> >
> > If I read my performance charts correctly, my aircraft (Piper Turbo
> > Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> > *true* airspeed for every 1000 feet you go up. Firstly, does that sound
> > about right to folks? I assume that this effect is from the decrease in
> > air friction at high altitudes (even though the prop also has less air
> > to "push on").
> >
> > So, unless there is some other factor, I think this means that if the
> > winds increase at anything higher than 2 nts per 1000 feet, I am best
> > off staying at the Minimum Enroute Altitude. Is that right?
> >
> > My experience thus far suggests that most of the time, the winds aloft
> > speed increase far faster then 2 nts per 1000 feet, so, in general, it
> > is unlikely that I will do much better than staying at the absolute
> > minimum altitude. Is that consistent with other folks' experience?
> >
> > -Sami
> >

O. Sami Saydjari > wrote:
: I went to Jeppeson's website and looked up flitestar. Looks like a nice
: software package. What I could not find is pricing information for the
: software or the subscription service to keep the charts updated and
: such. Can you give your view on the software and let us know what it
: retails for (including any subscriptions). Thanks.

For me, personally, I don't run Winders, so any downloadable packages don't
help me. That's why I use DUATS... web-based so it works everywhere. Oh, and it's
"free" (for AOPA members). Me the cheap *******... :)

-Cory

--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

Altitude is your friend. On the way to OSH last summer, we leveled off
at 10,000' (C172) after leaving BTV. A few minutes later, the engine
developed some serious roughness. It went away when I jammed the
mixture control in and pulled the carb heat. Then it came back. I was
about to declare an emergency when it cleared up for good. (I believe
that I had some water in the fuel that didn't hit the port until we were
in level cruise.) An event like that will certainly make you sit up
straight and start looking (my "copilot" had VERY wide eyes for a few
minutes). But at 10,000' (and my trusty handheld GPS), I had a couple
of airports within gliding distance (and lots of recently mowed hay
fields) to choose from. The remainder of the trip was uneventful (other
than the 2-day layover in Dayton to wait out the front).

For my IFR check ride, my DE asked me to plan a trip from CON (Concord,
NH) to HYA (Hyanis, MA). He asked why I selected 9000' feet for my
enroute altitude. Answer was, "In case I lose the engine." IMHO,
unless the headwinds are much stronger at 10-12K', I'd rather take a few
more minutes (OK, sometimes many more minutes) to get there, but have a
few more minutes and miles in case of an engine failure. My time is
just not that important.


Jeff wrote:
> I was thinking real hard about that glide distance the other day flying to
> phoenix.
> when passing over the colorado river area, I felt my plane kinda "surge", never
> felt it before, I thought the engine was surging but didnt see any indications
> on any of my instruments. I was looking around for a place to land and 8500 ft
> just didnt look high enough at the time.
> the trip was unevenful tho, I am thinking it was a gust of wind hitting me from
> behind making the plane surge forward for a second.
>
> Wyatt Emmerich wrote:
>
>
>>I travel about 8-10 thousand into the wind and 14-20 with the wind. I agree.
>>Usually the headwind increases faster than TAS with altitude. I travel 8-10
>>for safety--glide distance.
>>
>>"Jeff" > wrote in message
...
>>
>>>when I plan a flight against the wind (like a few days ago comming back
>>
>>from
>>
>>>phoenix) I go with the altitude that gives me the best ground speed.
>>>On my way back from phoenix at 8500 ft I had a GS of 130 kts, I had to go
>>
>>to
>>
>>>10500 for terrain and my GS went down to 117 kts., so I jumped back down
>>
>>to
>>
>>>8500 when I had the chance.
>>>
>>>Turbo airplanes take advantage of the thinner air up high is why they can
>>
>>go
>>
>>>faster then normally aspirated planes. you maintain your full 200 HP up to
>>
>>a
>>
>>>DA of 12,000 ft. So 12000 ft is where you start to lose horse power but
>>
>>the
>>
>>>air is thinner allowing you a better TAS and if you play the winds right,
>>>some really good ground speeds. stay low if you have a head wind, get up
>>>high when you have a tail wind.
>>>
>>>Sometimes, the wind down low will be higher then say around 10,000 or
>>
>>12000
>>
>>>ft or about the same. If there is not much difference in the winds, I
>>
>>would
>>
>>>select the higher altitude because of the thinnner air. Also you dont use
>>
>>as
>>
>>>much fuel up high.
>>>
>>>
>>>"O. Sami Saydjari" wrote:
>>>
>>>
>>>>When planning a flight against the wind, how to you pick the best
>>>>altitude when trying to minimize flight time?
>>>>
>>>>If I read my performance charts correctly, my aircraft (Piper Turbo
>>>>Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
>>>>*true* airspeed for every 1000 feet you go up. Firstly, does that sound
>>>>about right to folks? I assume that this effect is from the decrease in
>>>>air friction at high altitudes (even though the prop also has less air
>>>>to "push on").
>>>>
>>>>So, unless there is some other factor, I think this means that if the
>>>>winds increase at anything higher than 2 nts per 1000 feet, I am best
>>>>off staying at the Minimum Enroute Altitude. Is that right?
>>>>
>>>>My experience thus far suggests that most of the time, the winds aloft
>>>>speed increase far faster then 2 nts per 1000 feet, so, in general, it
>>>>is unlikely that I will do much better than staying at the absolute
>>>>minimum altitude. Is that consistent with other folks' experience?
>>>>
>>>>-Sami
>>>
>


--
Remove "2PLANES" to reply.

AOPA has an dumbed-down internet version of FlightStar that you can download
for free at:
http://www.aopa.org/flight_planner/intro.html

The Jepp North American IFR version of Flightstar V9.0 costs $239. I'm
running 8.0 and have never purchased the map or chart revision service. My
flight planning skills have atrophied as a result of using this thing. It
calculates flight times very accurately. But I like it best for long
x-country flights. You can draw a great circle between take-off and landing
and then drag your flight path up or down for fuel stops or VOR fly-overs or
to parallel victor airways if the weather sucks.


"O. Sami Saydjari" > wrote in message
...
> I went to Jeppeson's website and looked up flitestar. Looks like a nice
> software package. What I could not find is pricing information for the
> software or the subscription service to keep the charts updated and
> such. Can you give your view on the software and let us know what it
> retails for (including any subscriptions). Thanks.
>
> -Sami
>
> McGregor wrote:
> > Lazy people (like me) ask their computer. FlightStar from Jepp has an
> > "optimize altitude" function that is pretty handy. Once it has
downloaded
> > DUATs weather it will display groundspeed and fuel burn for all
altitudes
> > and highlight the optimal flight level.
> >
> > "O. Sami Saydjari" > wrote in message
> > ...
> >
> >>When planning a flight against the wind, how to you pick the best
> >>altitude when trying to minimize flight time?
> >>
> >>If I read my performance charts correctly, my aircraft (Piper Turbo
> >>Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> >>*true* airspeed for every 1000 feet you go up. Firstly, does that sound
> >>about right to folks? I assume that this effect is from the decrease in
> >>air friction at high altitudes (even though the prop also has less air
> >>to "push on").
> >>
> >>So, unless there is some other factor, I think this means that if the
> >>winds increase at anything higher than 2 nts per 1000 feet, I am best
> >>off staying at the Minimum Enroute Altitude. Is that right?
> >>
> >>My experience thus far suggests that most of the time, the winds aloft
> >>speed increase far faster then 2 nts per 1000 feet, so, in general, it
> >>is unlikely that I will do much better than staying at the absolute
> >>minimum altitude. Is that consistent with other folks' experience?
> >>
> >>-Sami
> >>
> >
> >
> >
>

Yes, I just tried the free version. It is quite nice (compared to the
one at DTC DUATS).

Thanks for the info on flitestar.

-Sami

McGregor wrote:
> AOPA has an dumbed-down internet version of FlightStar that you can download
> for free at:
> http://www.aopa.org/flight_planner/intro.html
>
> The Jepp North American IFR version of Flightstar V9.0 costs $239. I'm
> running 8.0 and have never purchased the map or chart revision service. My
> flight planning skills have atrophied as a result of using this thing. It
> calculates flight times very accurately. But I like it best for long
> x-country flights. You can draw a great circle between take-off and landing
> and then drag your flight path up or down for fuel stops or VOR fly-overs or
> to parallel victor airways if the weather sucks.
>
>
> "O. Sami Saydjari" > wrote in message
> ...
>
>>I went to Jeppeson's website and looked up flitestar. Looks like a nice
>>software package. What I could not find is pricing information for the
>>software or the subscription service to keep the charts updated and
>>such. Can you give your view on the software and let us know what it
>>retails for (including any subscriptions). Thanks.
>>
>>-Sami
>>
>>McGregor wrote:
>>
>>>Lazy people (like me) ask their computer. FlightStar from Jepp has an
>>>"optimize altitude" function that is pretty handy. Once it has
>>
> downloaded
>
>>>DUATs weather it will display groundspeed and fuel burn for all
>>
> altitudes
>
>>>and highlight the optimal flight level.
>>>
>>>"O. Sami Saydjari" > wrote in message
...
>>>
>>>
>>>>When planning a flight against the wind, how to you pick the best
>>>>altitude when trying to minimize flight time?
>>>>
>>>>If I read my performance charts correctly, my aircraft (Piper Turbo
>>>>Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
>>>>*true* airspeed for every 1000 feet you go up. Firstly, does that sound
>>>>about right to folks? I assume that this effect is from the decrease in
>>>>air friction at high altitudes (even though the prop also has less air
>>>>to "push on").
>>>>
>>>>So, unless there is some other factor, I think this means that if the
>>>>winds increase at anything higher than 2 nts per 1000 feet, I am best
>>>>off staying at the Minimum Enroute Altitude. Is that right?
>>>>
>>>>My experience thus far suggests that most of the time, the winds aloft
>>>>speed increase far faster then 2 nts per 1000 feet, so, in general, it
>>>>is unlikely that I will do much better than staying at the absolute
>>>>minimum altitude. Is that consistent with other folks' experience?
>>>>
>>>>-Sami
>>>>
>>>
>>>
>>>
>
>

wrote:

> For me, personally, I don't run Winders, so any downloadable packages don't
> help me. That's why I use DUATS... web-based so it works everywhere. Oh, and it's
> "free" (for AOPA members). Me the cheap *******... :)

Just for the record, you don't need to be an AOPA member to get DUAT for free.

http://www.duats.com DynCorp DUAT
http://www.duat.com DTC DUAT

If you like telnet access: "telnet direct.duats.com". Easy to create a text log
of your DUAT session that you can edit, so it's easier to print selected parts
of the briefing to take with you.

http://www.enflight.com gives you some html post-formatting of the DUAT output
that I find useful. Actually I think this is what AOPA uses under-the-covers.

All are free.

Dave (another Winders avoider and cheap *******)
Remove SHIRT to reply directly.

"O. Sami Saydjari" > wrote in
:

> When planning a flight against the wind, how to you pick the best
> altitude when trying to minimize flight time?
>
> If I read my performance charts correctly, my aircraft (Piper Turbo
> Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
> *true* airspeed for every 1000 feet you go up.

That's right... 2 knots increase in TAS per 1000 feet MSL is a rough
guideline, but good enough for calculations. Note that this only holds
true, however, for altitudes where you can hold the same power output.
This means, all other things being equal, that the most efficient
altitude is the maximum one at which you can still output your desired
power. For a normally aspirated aircraft flying at 75% or 65% power, we
are looking at between 5500 and maybe 8500 feet MSL.

For your turbo Arrow it depends on the condition of your turbocharger
and whether you have a Merlyn wastegate or not. With a Merlyn you can
easily hold 75% well up into the flight levels.

> So, unless there is some other factor, I think this means that if the
> winds increase at anything higher than 2 nts per 1000 feet, I am best
> off staying at the Minimum Enroute Altitude. Is that right?

Right, but only a small part of the story. How bad is the thermals and
other turbulence at the altitude you want to fly. How hot is it? [In
Texas we often see 80+ degrees at 10,000 or higher.] Are you out
sightseeing, or trying to get somewhere. Icing? Thunderstorms around
(and do you have 'sferics equipment on board). How far are you going
(is it worth the time/fuel to climb)? Other reason to want to climb
high? [Like bad terrain at night.] Do your passengers like sucking on
an O2 hose?

And of course, which way is the wind blowing!!!

Lots of things to consider, and often not just one "right" answer.

Purely my own habit (also in a turbo Arrow III) I will fly anything over
an hours trip at least around 10,000 unless there is a big reason no to
(high winds). Gives good speed and ride (usually) without too much
time-to-climb. Over that, especially if by myself, I will climb up to
the O2 levels (again, depending upon wind). Long trips - ALWAYS go high
unless you are really fighting a massive headwind.

This time of the year, flying from Austin to El Paso (450 nm west of
here) in the winter (winds almost always out of the west up high) - I
will fly out there (west) at around 10K. That gives me acceptable
headwinds, while still keeping me high enough over the Davis mountain
range to avoid most turbulence. Coming back I will climb into the
flightlevels, pull back the power, and look for a 75+ knot tailwind.
[One trip I had a nice 250 - 275 knot groundspeed, on 55% power!!!]

BTW, some years ago I put all my flight characteristics into a small
computer program and just sat there playing with the results. For a
flight of X miles was it faster to climb to Y altitude, etc. Taking
into account the slower climb, the faster cruise, and the glide -
figured time and fuel. [Remember, this is always a no-wind simulation,
since it was a hypothetical trip.]

The results was not what I expected. Turned out that for anything much
over about 50 miles higher was pretty much always better. Time was
shorter the higher you went (descent doesn't buy back all the time you
lose on the climb, but it gets back a LOT of it). Fuel burn was
minimized at the highest altitude where you had anything over 1/3rd of
your time in cruise.


--
-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------